BERTHOLD TECHNOLOGIES LB 444 - 7.3 Function of Temperature Compensation

04/03 347 LB 444
50
7.3 Function of Temperature Compensation
The temperature coefficient of a liquid is not constant over a large temperature range,
but usually it increases with rising temperatures. Temperature compensation is carried
out according to the following formula:
ρ
Ref
= ρ
M
+ (ϑ
P
- ϑ
Ref
) · TC
1
+ (ϑ
P
- ϑ
Ref
)
2
· TC
2
ρ
Ref
= Density value compensated relative to reference temperature
TC
1
= Linear temperature coefficient TC
1
TC
2
= Square temperature coefficient TC
2
ρ
M
= Measured density value
ϑ
P
= Product temperature
ϑ
Ref
= Reference temperature
(Terms in italics refer to parameters that have to be entered in the Product Data menu).
With minor temperature changes (approx. ± 20°C) it suffices, in most cases, to enter the
linear coefficient.
7.4 Temperature Compensation in Suspensions
The characteristic temperature curve of water is used for measurement of suspensions
with water as carrier liquid.
Proceed as follows:
In the Calibrate menu, select the function Suspension measure and Water TC.
Then you just have to enter the reference temperature.
A temperature coefficient need not be entered.
7.5 Calculation of Temperature Coefficients
Example:
Product: HCl - water mixture
Measuring range: 20 - 40 weight % HCl
Temperature range: 10° - 30° C
Unit of measure: g/cm
3
The temperature coefficient at average concentration (30%) is calculated as follows:
0.00059 =
3010
1.1433 -1.1551
- =
-
-
- = TC
21
21
− ϑϑ
ρ
ρ
ρ
1
= Density in g/cm
3
at ϑ
1
ρ
2
= Density in g/cm
3
at ϑ
2
Input value: 5.9000e-04